Although it has fallen into common usage as meaning mass destruction, decimated truly means nothing of the sort.
Decimated means one in ten destroyed, not nine out of ten.
If you have a general declare his troops decimated the opposing army, you are actually having him say he ruined 10% of their forces.
If your general were to say something like he only lost one in four of his men while decimating half of the enemy’s army, he would actually be saying he lost 25% of his men to destroy 10% of 50% of the enemy forces, or only 5% overall.
Not really much of a victory after all.
You can find more tidbits in my book on self-editing, Blood From Your Own Pen!